Depth control in well operations



BZQLZOO Dec. H3, 1966 J. w. KENNEDAY DEPTH CONTROL IN WELL OPERATIONS 2 Sheets-Sheet 1 Filed Dec. 19, 1960 FIG-5.

INVENTOR.

JOHN W- KEN EDAY. A

FlG. 4.

ATTORNEY.

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LOG RUN m Wuj J. W- KENNEDAY DEPTH CONTROL IN WELL OPERATIONS COLLAR LOG\ RADIOACTIVE P PILL I50 INVENTOR.

JOHN W. KENNEDAY, w am ATTORNEY.

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Dec. 13, 1966 Filed Dec. 19, 1960 United States Patent 3,291,208 DEPTH CONTROL IN WELL OPERATIONS John W. Kenneday, Corpus Christi, Tern, assiguor, by

mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed Dec. 19, 1960, Ser. No. 76,717 8 Claims. (Cl. 166-4) The present invention concerns a method of depth control in well operations and particularly for operations in wells containing a multiplicity of pipe strings. It is especially applicable in multiple tubingless completions. In these type completions a plurality of pipe strings are set in a well bore, the pipe strings and productive formations penetrated by the well bore are perforated, and each formations fluids are produced independently through the individual pipe strings.

In order to obtain accurate depth control in completions, recompletions, or work-over operations conducted in wells, it is conventional practice to make a radioactivity survey of the well to locate positions of subsurface productive formations together with a pipe string collar cator log to indicate positions of the pipe string collars. Correlating positions of the pipe string collars and the positions of the productive formations in this manner permits work tools, e.g., perforator guns, to be accurately positioned in the well adjacent any particular productive formation by lowering the work tool together with a pipe string collar locator logging device the distance determined by the number of pipe string collar indications between the surface of the earth and the particular formation as established by the original pipe string collar locator and radioactivity survey correlation log. In wells containing two or more spaced-apart, parallelly extending pipe strings, it is necessary to obtain the correlating pipe string collar locator and radioactivity survey log for each pipe string to accurately establish locations of the productive formations relative to locations of the pipe string collars, because the conventional pipe string collar locator device detects only the collars of the pipe string through which it is run. On the other hand, if the collar locator device detected the collars of adjacent pipe strings, there would be no way to distinguish the collars of one pipe string from those of the other pipe strings. Therefore, it is necessary to restrict detection of the collars to the pipe string through which the pipe collar locator device is run.

When operating in these type wells, it is expensive and time consuming to obtain the required radioactivity survey and pipe string collar locator logs for each pipe string. A procedure which minimizes cost and time consumed in operations of this nature is provided by the present invention. In the technique covered by the method of the invention, at least one indicator, e.g., a radioactive substance, is positioned in one or more pipe collars of the pipe string or pipe strings other than the pipe string in which the correlation pipe string collar 10- cator and radioactivity survey log is to be made; that is, one of the pipe strings is left unmarked, and the other remaining pipe strings are marked with a radioactive material. Then when the radioactivity survey is made in the unmarked pipe string, the positions of the radioactive material spotted in the collars of the other pipe strings are located relative to the locations of the producing formations. To accurately position a tool adjacent a particular formation when operating in any one of the marked pipe strings, it is only necessary to lower the tool along with a pipe string collar locator to adjacent the pipe collar nearest to the depth of the marker as established by the original radioactivity survey and then raise or lower the tool to the particular formation the distance between the marker and the formation as shown by the "ice original radioactivity survey log. If desired, all of the pipe strings could be marked in this manner and the same procedure used to position a tool in any of the pipe strings; however, it is easier to position a tool in the pipe string in which the radioactivity survey is taken in accordance with the previously described conventional procedure.

By properly spacing the radioactive material in the marked pipe strings, the identity of each can be clearly ascertained. However, to avoid any possibility of confusion as to the identity of a particular pipe string, different lengths of pup joints for each marked pipe string may be strategically located along the lengths of the pipe strings, and the radioactivity markers placed in the collars of the pup joints. Thus, in one pipe string, two-foot pup joints may be arranged; .in another pipe string, fourfoot pup joints may be used, etc.

Thus, a primary object of this invention is to provide an improved method for more accurately maintaining depth control for well operations conducted in wells containing a plurality of spaced-apart, parallelly extending pipe strings.

The above object and other objects of the invention will be apparent from a more detailed description thereof when taken in conjunction with the drawings wherein:

FIG. 1 is a cross-sectional view of the earths subsurface showing a well bore penetrating a plurality of producing formations and containing a plurality of pipe strings, two of which are provided with radioactive markers.

FIG. 2 is a cross-sectional view of one of the pipe strings shown in FIG. 1 showing arranged in it pipe collar detector and induced gamma ray logging apparatus;

FIG. 3 is also a cross-sectional view of one of the pipe strings shown in FIG. 1 showing a pipe collar having a radioactive pill inserted in it;

FIG. 4 illustrates a representative pipe collar and radioactivity survey log made in the unmarked pipe string;

FIG. 5 is a cross-sectional view of one of the pipe strings shown in FIG. 1 showing suspended in it a gun perforator assembly including radioactivity gun orienting elements and also a pipe collar locator device;

FIG. 6 illustrates a pipe collar locator log made in one of the marked pipe strings of FIG. 1;

FIG. 7 is a view similar to that shown in FIG. 1 illustrating a modified arrangement of the radioactivity markers;

FIG. 8 illustrates a representative pipe collar and radioactivity survey log made in the unmarked pipe string of FIG. 7;

. FIG. 9 is a view similar to that shown in FIG. 3 illustrating the modified radioactivity marker arrangement of FIG. 7; and

FIG. 10 is a cross-sectional view of one of the pipe strings illustrating one manner of spotting radioactive material in a pipe string.

In FIG. 1 is shown a borehole 10 penetrating three subsurface productive formations A, B, and C. Three pipe strings, 11, 12, and 13, are arranged in borehole 10 and cemented therein. Pipe strings 12 and 13 are provided with radioactivity markers 15 and 16, respectively, strategically positioned near productive formations B and A, respectively. Pipe string 11 extends the length of borehole 10 to adjacent the lowermost formation C; pipe string 12 extends to adjacent intermediate formation B; and pipe string 13 only extends to adjacent the uppermost formation A. Although this particular arrangement has been used to illustrate the invention, if desired, all of the pipe strings may extend the length of the borehole to adjacent formation C. Also, although only one marker 15, 16 is provided in each pipe string 12 and 13, additional markers spaced apart a few hundred feet may 3 be used. It is preferred to place the markers at points other than adjacent the productive formations in order to avoid possible confusion during subsequent gun orienting operations or other operations involving use of radioactive materials.

The radioactivity markers are placed or spotted in the collars of the pipe strings. As seen in FIG. 3, pipe collar 17 of pipe string 12 has positioned in it a radioactive pill or capsule 15. However, if desired, the radioactive material may be painted on the collar or joint, or radioactive thread dope may be used in making up the pipe joints, or any other desired manner of application of the radioactive material may be used so long as the radioactive material is located in the pipe string collar or joint.

As seen in FIG. 10, the markers may be temporarily positioned in the pipe collars. In this figure a radioactive pill 15 is attached to or positioned in a conventional collar stop device 18, which may be positioned in and retrieved from pipe collar 17 of pipe string 12 by means of wire line tools.

The radioactive material of the marker may have a short or relatively short half-life; such as iodine 131, 8.04 days; tantalum 182, 115 days; thorium 228, 1.9 years; antimony 126, 9 hours; antimony 119, 39 hours; or longer half-life materials such as uranium 238, 4.498 10 years; radium series 226, 1620 years; octanium 228, 27.7 years; thorium 230, 8 10 years; potassium isotope 40, 1.4x 10 years. Relatively weak radioactive material may be used if desired.

To illustrate the invention, a multiple tubingless completion operation will be described. In completion operations when more than one pipe string is positioned adjacent a productive formation it is desired to perforate, it is necessary to direct the fire of the gun elements in a direction so as to avoid striking and damaging one or more of the pipe strings extending parallel to the pipe string through which the gun perforator assembly is lowered. One method for directing the fire of gun penforator elements, i.e., for orienting the gun, utilizes radioactivity detection techniques. In one of these a radiation detector and a source of bombarding radiation are positioned in the pipe string through which the production fluids are to be conducted to the surface, and the radiation resulting from bombardment by the source radiation is detected as described and claimed in US. patent application SerialNo. 780,524, filed December 15, 1958, by Harry S. Arendt, entitled Method and Apparatus for Operating in Wells. It is this technique that is described in the description of the method of the invention. FIG. shows this apparatus which includes a rotatable assembly 30, consisting of gun elements 31, a focused source of radiation 32 (instead of focusing the source of radiation, the detector of radiation could be focused so as to detect radiation in only one direction), a radiation shield 33 designed to prevent the bombarding source of radiation 32 from being detected directly by the detector of radiation 34 positioned above shield 33, and a rotator 35 provided with a plurality of centralizers and restrainers 36, suspended on a wire line 37, which is attached at its upper end to a recorder 38 and fire control apparatus 39. Also, a collar locator detector device 40 is arranged on assembly 30; however, this device is not used in the gun orientation operation. Other gun orienting techniques of this type may be employed for orienting the gun; as for example, the technique in which a radiation detector is arranged in the pipe string to be detected, and a radiation source is positioned in the pipe string through which the fluids are to be produced and the direct focused primary radiation from the source is detected by the detector. U .S. patent application Serial No. 780,517, filed December 15, 1958, by James T. Br-umble, Jr., entitled Method and Apparatus for Well Operations, shows and describes this orienting technique.

The general procedure for practicing the method of the invention is as follows. Borehole 10 is formed and penetrates producing formations A, B, and C. Then a conventional electrical resistivity log .may be run in the open borehole to establish the depth locations of productive formations A, B, and C. Pipe strings 11, 12, and 1.3 then are run and landed and cemented in borehole 10. Pipe strings 12 and 13 may be spotted with radioactive markers 15 and 16, respectively, prior to running the pipe strings into borehole 10. However, if the radioactive material is not placed in the collars prior to running of the pipe strings, then temporary radioactive markers may be positioned in the particular pipe collars. The particular pipe collars selected are preferably those adjacent the formations, the fluids of whidh are to be produced through that pipe string. As mentioned previously, FIG. 3 illustrates penmanently positioning radioactive material 15 in the pipe collar, and FIG. 10 illustrates an arrangement in which the radioactive mate rial 15 may be temporarily placed in the pipe string. Once the radioactive material has been placed in the particular pipe collar of interest, whether temporarily or permanently, a pipe collar locator logging tool and a conventional gamma-gamma or gamma-neutron logging tool, such as the assembly 41 suspended in pipe string 11 on a cable 42 as seen in FIG. 2, is used to traverse pipe string 11 and log the borehole. The elements of assembly 41 include a pipe collar detector device 43, a bombarding source of radiation 44, a shield 45, and a detector of radiation 46. Shield 45 prevents the detection of direct radiation emanating from the source 44 by detector 46. Both collar detector devices 40 and 43 may be of the magnetic type. Cable 42 connects to a recorder 47, which records a pipe collar log 48 and a radioactivity log 49, as shown in FIG. 4. Pips 48' on pipe collar log 48 indicate the joints or collars of pipe string 111. On the radioactivity survey log 49 the radioactivity marker 16 is indicated by the pip 16', and the radioactivity marker 15 in pipe string 12 is indicated by the pip 15'. The formations A, B, and C are indicated by the change in the log as at A, B, and C.

Once the logs of FIG. 4 have been recorded, the radioactive materials 15 and '16 are no longer needed. Thus, the radioactive material may be of a very short halflife, or it may be but temporarily placed in the pipe collar.

When it is desired to perforate the lowermost producing formation C, it is only necessary to lower a gun perforator together with a collar locator device to the depth of formation C as established by the original correlative radioactivity log 49 and pipe collar locator log 48. That is, the proper depth is reached when the same number of pipe collars between the surface and formation C are counted off on the pipe collar log run with the gun perforator. Since there are no intervening pipe strings in any direction surrounding pipe string 11 adjacent formation C, it is not necessary to orient the gun perforator in any particular direction.

When it is desired to perforate formations A or B, it is necessary to orient the gun perforator to direct the fire thereof in a direction so as to avoid striking one or more of the adjacent parallel pipe strings. Also, to perforate either of these formations, it is necessary to position the [gun perforator at the proper depth. Thus, to perforate formation B the assembly 30 of FIG. 5 is lowered on wire line 37 through pipe string 12 to a depth of 4960 feet, which is the depth of the radioactive material 15, as shown at 15' on the radioactivity survey log. 49. Also, collar detector 40 records on recorder 38 the pipe collar log 50 shown in FIG. 6. Pips 51 indicate the collars of pipe string 12. It is seen from this log that there is a collar located at 4967 feet and another collar at 4938 feet. Since the collar at 4967 feet is closest to the depth of 4960 feet, estabilshed as the radioactivity marker 15 on the radioactivity survey log 49, it must be the collar in v (5000 feet minus 4960 feet), as determined from the radioactivity log 49, to formation B. Then the gun elements are directed so as to fire in a direction away from pipe string 11 according to known techniques, and the gun is fired by the fire control 39 at the surface. Formation A is perforated in a similar manner, except the gun elements 31 are directed away from both pipe string 11 and 12 prior to firing thereof.

FIGS. 7, 8, and 9 illustrate a similar operation. However, the pipe strings are more positively identified by employing pup joints of different lengths for different pipe strings. In FIG. 7 borehole ltl has arranged in it pipe strings 11, 12a, and 13a. As seen more clearly in FIG. 9, the radioactive material 15a is spotted in the pipe collars 17a of a short length of pipe or pup joint 60 of a selected length, e.g., four feet. As shown in FIG. 9, the radioactive material may be in the form of a pill or capsule, as illustrated also in FIG. 3. In pipe string 13a a similar arrangement of the radioactive material is provided; i.e., the radioactive material 16a is spotted in the collars at the ends of a short length of pipe or pup joint 61. However, in this instance, the length of the joint is different from the length of joint 60; e.g., it may be an 8-foot joint or a 2-foot joint. The difference in the lengths of the joints permits ready distinction among the pipe strings. The correlative pipe collar log and radioactivity survey log taken by the instrumentation shown in FIG. 2, similar to the logs of FIG. 4, are illustrated in FIG. 8. Thus, as before, log 48 and pips 48' indicate the positions of the collars of pipe string 11. The radioactivity survey log 62 is different from the radioactivity survey log 49 of FIG. 4, and in this log are shown the pips 16a, which evidence the 8-foot joint 61 of pipe string 13a, and pips 15a evidence the 4-foot pipe joint 60 of pipe string 12a. The operation is the same with regard to this embodiment; however, by using pup joints of different lengths, the identity of the pipe string is more positively established, and there should be no question about which pipe string the operations are being conducted in. Also, when depth measurements are sufficiently in error as to permit a choice of collars the radioactive collar may be positively selected by pup joint length.

Although the logs of FIG. 4, 6, and 8 illustrate collar pips picked up by the collar detectors, it will be understood that these conventional collars have not been shown in FIGS. 1 and 7 for reasons of clarity. Only the radioactive collars have been shown.

The sources of radiation for elements 44 and 32 may be fast neutrons or gamma rays. The neutron source may be the result of an alpha neutron, deuteron neutron, or proton neutron reaction in which the alpha particle, deuteron, or proton is accelerated by an electric field and caused to interact with selected target materials in order to produce neutrons of various energies. Or the source may be neutrons originating from radium beryllium or polonium beryllium. Also, high energy gamma radiation sources which may be employed are radioactive Na 24, La 140, Sb 124, C 60, or high energy gamma rays produced by various reactions in high energy particle machines in manners well known to the art of nuclear physics.

Detectors 46 and 34 may be used to detect slow neutrons or gamma rays or fast neutrons, and for the detection of these types of radiation, ionization chambers, Geiger-Muller tubes, and scintillation counters may be used. The moderating shields 45 and 33 are formed of radiation-absorbing or moderating materials such as lead, tungsten, paraffin, boron, cadmium, etc., which materials are capable of absorbing the radiation falling onto it.

Having fully described the method, apparatus, and objects of my invention, I claim:

1. A method of depth control for a well operation in a well penetrating at least two productive formations and containing at least two juxtaposed pipe strings comprising: temporarily positioning in at least one pipe collar of one pipe string a radioactivity marker; running in said other pipe string a radioactivity survey tool together with a collar locator tool and preparing therefrom a correlation log showing the locations of said formations, the locations of the pipe collars of said other pipe string, and the position of said radioactivity marker, relative to each other; removing said marker from said one pipe string; running in said one pipe string a well tool together with a collar locator tool and preparing :a log showing the pipe collars of said one pipe string; moving said well tool and said collar locator tool vertically to the pipe collar in said one pipe string nearest in depth to the depth of said radioactivity marker as shown on said correlation log; and then moving said well tool and said collar locator tool the distance between one of said formations and said radioactivity marker as shown on said correlation log to position said well tool in said one pipe string adjacent said one formation.

2. A method as recited in claim 1 in which said well operation is perforating and said well tool is a perforator and including actuating said perforator to perforate said one formation after positioning said well tool perforator adjacent said one formation.

3. A method as recited in claim 1 including employing as said radioactive marker a short half-life radioactive material.

4. A method of depth control for -a well operation in a well penetrating at least two productive formations and containing at least two juxtaposed pipe strings, one of which contains in at least one pipe collar thereof a radioactivity marker comprising: running in said other pipe string a radioactivity survey tool together with a collar locator tool and preparing therefrom a correlation log showing the locations of said formations, the locations of the pipe collars of said other pipe string, and the position of said radioactivity marker, relative to each other; running in said one pipe string a well tool together with a collar locator tool and preparing a log showing the pipe collars of said one pipe string; moving said well tool and said collar locator tool vertically to the pipe collar in said one pipe string nearest in depth to the depth of said radioactivity marker as shown on said correlation log; and then moving said well tool and said collar locator tool the distance between one of said formations and said radioactivity marker as shown on said correlation log to position said well tool in said one pipe string adjacent said one formation.

5. A method as recited in claim 4 in which said well operation is perforating and said well tool is a perforator and including actuating said perforator to perforate said one formation after positioning said well tool perforator adjacent said one formation.

6. A method as recited in claim 4 including employing as said radioactive marker a short half-life radioactive material.

7. A method of depth control for perforating in a well penetrating at least three upper, intermediate, and lower productive formations and containing at least three first, second, and third juxtaposed pipe strings, at least two of which, viz, said second and third pipe strings, contain in at least one pipe collar an identifiable radioactivity marker comprising: running in said first pipe string a radioactivity survey tool together with a collar locator tool and preparing therefrom a correlation log showing the locations of said formations, the locations of the pipe collars of said first pipe string, and the positions of said radioactivity markers of said second and third pipe strings, relative to each other; lowering a perforator in said first pipe string to the depth of said lower formation as determined from said correlation log; actuating said perforator to perforate said lower formation in order to produce it independently through said first pipe string; running a well tool in said second pipe string together with a collar locator tool, said well tool including a perforator having a selected direction of perforation and radiation means having a selected direction of pipe detection and preparing a log showing the pipe collars of said second pipe string; moving said well tool and said collar locator tool vertically to the pipe collar in said second pipe string nearest in depth to the depth of said radioactivity marker of said second pipe string as shown on said correlation log; further moving said well tool and said collar locator tool the distance between said intermediate formation and said radioactivity marker of said second pipe string as shown on said correlation log to position said well tool adjacent said intermediate formation; rotating said well tool to locate with said radiation means the radial positions of said first and third pipe strings relative to the direction of perforation, further rotating said well tool to direct the direction of perforation of said perforator away from said first and third pipe strings; actuating said perforator to perforate said intermediate formation in order to produce said intermediate formation independently through said second pipe string; running in said third pipe string said well tool and said collar locator tool and preparing a log of the pipe collars of said third pipe string; moving said well tool and said collar locator tool vertically to the pipe collar in said third pipe string nearest in depth to the depth of said radioactivity marker of said third pipe string as shown on said correlation log; further moving said well tool and said collar locator tool the distance between said upper formation and said radioactivity marker of said third pipe string as shown on said correlation log to position said well tool adjacent said upper formation; rotating said Well tool to locate with said radiation means the radial positions of said first and second pipe strings relative to the direction of perforation; further rotating said well tool to direct the direction of perforation away from said first and second pipe strings; and then actuating said perforator to perforate said upper formation in order to produce it independently through said third pipe string.

8. A method of depth control for a well operation in a well penetrating at least two productive formations and containing at least two juxtaposed pipe strings, one

8 of which contains in at least one pipe collar thereof a radioactivity emitting marker comprising:

running in said other pipe string a radioactivity survey tool together with a collar locator tool and preparing therefrom a correlation log showing the locations of said formations, the locations of the pipe collars of said other pipe string, and the position of said radioactivity emitting marker, relative to each other;

running in said one pipe string a well tool together with a collar locator tool and preparing a log showing the pipe collars of said one pipe string;

moving said well tool and said collar locator tool vertically to the pipe collar in said one pipe string nearest in depth to the depth of said radioactivity emitting marker as shown on said correlation log; and

then moving said well tool and said collar locator tool the distance between one of said formations and said radio-activity emitting marker as shown on said correlation log to position said well tool in said one pipe string adjacent said one formation.

References Cited by the Examiner UNITED STATES PATENTS 2,147,544 2/1939 Potts 166-66 2,228,623 1/1941 Ennis 1664 2,316,361 4/1943 Piety 250-83.6 2,320,890 6/1943 Russell 16666 X 2,350,832 6/1944 Segesman 1664 2,476,136 7/1949 Doll 1664 2,476,137 7/1949 Doll 1664 2,710,925 6/1955 McKay --41 X 2,768,684 10/1956 Castel et al. l6655.5 2,842,852 7/1958 Tanguy 1664 X 2,871,946 2/1959 Bigelow 16664 2,998,068 8/1961 True 16655 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

C. D. JOHNSON, D. H. BROWN, Assistant Examiners. 

4. A METHOD OF DEPTH CONTROL FOR A WELL OPERATION IN A WELL PENETRATING AT LEAST TWO PRODUCTIVE FORMATIONS AND CONTAINING AT LEAST TWO JUXAPOSED PIPE STRINGS, ONE OF WHICH CONTAINS IN AT LEAST ONE PIPE COLLAR THEREOF A RADIOACTIVITY MARKER COMPRISING: RUNNING IN SAID OTHER PIPE STRING A RADIOACTIVITY SURVEY TOOL TOGETHER WITH A COLLAR LOCATOR TOOL AND PREPARING THEREFROM A CORRELATION LOG SHOWING THE LOCATIONS OF SAID FORMATIONS, THE LOCATIONS OF THE PIPE COLLARS OF SAID OTHER PIPE STRING, AND THE POSITION OF SAID RADIOACTIVITY MARKER, RELATIVE TO EACH OTHER; RUNNING IN SAID ONE PIPE STRING A WELL TOOL TOGETHER WITH A COLLAR LOCATOR TOOL AND PREPARING A LOG SHOWING THE PIPE COLLARS OF SAID ONE PIPE STRING; MOVING SAID WELL TOOL AND SAID COLLAR LOCATOR TOOL VERTICALLY TO THE PIPE COLLAR IN SAID ONE PIPE STRING NEAREST IN DEPTH TO THE DEPTH OF SAID RADIOACTIVITY MARKER AS SHOWN ON SAID CORRELATION LOG; AND THEN MOVING SAID WELL TOOL AND SAID COLLAR LOCATOR TOOL THE DISTANCE BETWEEN ONE OF SAID COLLAR LOCATOR SAID RADIOACTIVITY MARKER AS SHOWN ON SAID CORRELATION LOG TO POSITION SAID WELL TOOL IN SAID PIPE STRING CENT SAID ONE FORMATION. 